Hereinafter, the background art and its problem will be described.
Generally, in a fuel injection pump used in a marine engine, an ignition delay phenomenon may occur due to a use of bunker-C (HFO) having a different viscosity for each fuel such that compensation is needed for a combustion loss, and a technique for compensating the combustion loss is, in a large sense, collectively called as a variable injection timing (VIT) technique and, in substance, refers to a technique which achieves optimized combustion by performing compensation using fuel quality setting (FQS).
The VIT or the FQS described above is used for purpose of reducing a fuel cost while improving combustion efficiency by increasing a maximum combustion pressure within a combustion cylinder.
Generally, the VIT may automatically adjust an injection timing during an operation of an engine and allows optimal fuel consumption at a low load.
Generally, in a fuel injection pump of a bosch type, a plunger blocks a spill port of a barrel such that a pressure of fuel begins to rise and fuel of a high pressure is injected, and in this case, in order to control a fuel injection start timing, a location of the spill port formed on the barrel is adjusted vertically or a shape of the plunger is modified according to a load.
However, in the general conventional VIT technique which adjusts a fuel injection timing, a separate apparatus having a complex structure which changes the location of the spill port of the barrel needs to be installed or the shape of the plunger is modified in complexity such that, when the plunger is worn out or a material property of the fuel, a problem exists in that the fuel injection timing is changed and the fuel injection timing is difficult to be controlled externally.